The installation of the hundreds of muon chambers in the central (barrel) detector has started:

Installation of a barrel muon station. (Image: ATLAS Experiment/CERN)

First end-cap calorimeter assembled:

The rear of the electromagnetic end-cap calorimeter wheel in its final position in the cryostat. In the foreground is the edge of the front HEC wheel, in the process of being slid into the cryostat. (Image: ATLAS Experiment/CERN)

The central "barrel" calorimeter was moved from its assembly point at the side of the ATLAS cavern to the centre of the detector (within toroidal magnet system). The detector was aligned, to a precision of less than a millimetre:

The central calorimeter near the center of the ATLAS detector. (Image: ATLAS Experiment/CERN)

The set of eight barrel toroid magnets that enclose much of the ATLAS detector has been released from the temporary supports and is now mechanically self-supporting:

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Barrel toroid magnets in their final positions. Note figure at bottom center for scale. (Image: Maximilien Brice/CERN)